Plunger lift for wells



Feb. 13, 1962 E. E. ROACH ETAL 3,020,852

PLUNGER LIFT FOR WELLS Filed April 17, 1958 2 Sheets-Sheet 1 [Ask/He 5 Race/2 [var] VV. Baker INVENTORS ATTORNEY Feb. 13, 1962 E. E. ROACH EFAL 3,020,852

PLUNGER LIFT FOR WELLS Filed April 17, 1958 2 Sheets-Sheet 2 J9 5 42 /"JA//7 E. Roach [Va/7 l V. Ba/rer' INVENTORS A TIER/V6 r United States Patent 3,020,852 PLUNGER LIFT FOR WELLS Erskine E. Roach and Ivan W. Baker, Houston, Tex., assignors to Harold Brown Company, a corporation of Texas Filed Apr. 17, 1958, Ser. No. 729,171 14 Claims. (Cl. 103-225) This invention relates to free-piston pumping systems, also commonly called plunger lift systems, for producing oil wells, and more particularly to improvements in the piston or plunger element of such systems. In general, a free piston comprises a tubular body which is insertible in a well tubing and carries means adapted to form a slidable seal with the wall of the well tubing, and is provided with valving apparatus for opening and closing the bore of the piston body during its movements between the bottom and the top of the well. Fluid pressure in the well is employed to drive the piston to the surface in order to lift a charge of oil and other well fluid which enters the well tubing from the surrounding earth formations.

In a co-pending application of Everett D. McMurry, Serial No. 585,881, filed May 18, 1956, now Pat. No. 2,878,754, there is disclosed a form of free-piston or plunger having as one of its primary features the employment of a plurality of relatively flat individual rings, annularly dimensioned to be loosely mounted about the plunger body so as to form an adjustable seal between the plunger and the wall of the well tubing. By the use of a pluralityof individual rings, so mounted, this plunger overcomes many of the-disadvantages of other more conventional plunger lift devices in providing a more efiicient seal between the plunger and the tubing wall. The individual rings, which are relatively short in their axial dimension, are unrestricted in their lateral and angular movements within the limits of the annular clearance between their inner peripheries and the exterior of the plunger body, in order that they may assume random radialand angular positions relative to each other between the plunger body and the tubing wall. The freedom thus permitted the ring movement is intended to assure efiective closure of the annular space between the plunger and the tubing wall while permitting the plunger to pass freely over accumulations of parafiin and other projections which may be present on the tubing wall through retraction of the rings from the projections thus encountered.

However, it has been found that the lack of restriction on the radial and angular movement of the loose rings may in some cases cause the rings to line up in uniform angular relation under stream-lining action of the fluids in the well, and may have the result of forming relatively unobstructed passages between the plunger and the tubing wall through which substantial leakage of fluid past the plunger may occur, thereby reducing its lifting efiiciency.

The present invention is directed primarily to improvements in plungers of the loose ring type, above described, in providing means for positively but yieldably urging each of the rings to a radially off-set position relative to the longitudinal axis of the plunger body, the rings being urged to difierent and generally pre-determined an- 3,020,852 Patented Feb. 13, 1962 gular positions relative to each another. In accordance with this invention, by thus applying a positive force tending to urge the several rings away from the plunger body and toward the surrounding well tubing at different and generally predetermined angular positions, the sealing effectiveness of the group of rings, as a whole, is greatly enhanced, and the disadvantages of earlier types, above described, are largely overcome.

Various means may be employed in accordance with the present invention for yieldably urging the rings to the eccentric or off-set positions relative to the axis of the plunger body and to each other. In accordance with the several illustrative embodiments, the means employed to accomplish the desired purpose may comprise springs or may be magnetic means, both of which, functionally, may be considered to be elastic means, as will appear more fully hereinafter.

The several objects and advantages of this invention will become more readily apparent from the following detailed description when read in conjunction with the accompanying drawing which illustrates several useful em-. bodiments in accordance with this invention.

In the drawing:

FIG. 1 is an elevational view, illustrating a plunger of the general type contemplated for use with the present invention and showing the same in position in a well tubing as the plunger approaches the lower limit to its downward movement in the tubing; I

FIG. 2 is an elevational view, partly in section, of a plunger of the type shown generally in FIG. 1, illustrating details of the construction of the sealing rings in accordance with one embodiment of this invention;

FIG. 3 is a cross-sectional view taken generally along line 3-3 of FIG. 2;

FIG. 4 is an elevational view of a portion of a plunger of the general form illustrated in FIGS. 1 to 3, il1ustrat-- ing another form of ring in accordance with another em-- bodiment of the present invention;

FIG. 5 is a cross-sectional view taken generally along. line 55 of FIG. 4;

FIG. 6 is a fragmentary view, similar to FIG; 4, illustrating another modification of sealing ring construction and arrangement in accordance with this invention;

FIG. 7 is a cross-sectional view taken generally along line 77 of FIG. 6; and

FIG. 8 is a cross-sectional view, similar to FIG. 3, il-' lustrating a modification of the structure illustrated in FIGS. Zand 3. 1

Referring to the drawings and to the general arrangement illustrated in FIG. 1, there is shown a well tubing T, forming the production tubing of an oil well (not shown) from which well fluids are to be produced by' means of a free piston or plunger, designated generally by the numeral 10, the tubing string being provided with performations 11 through which well fluids enter the tubing string from the surrounding earth strata. A spring supported stop 12 is shown positioned in the lower portion of the tubing string to be engaged by the plunger at the terminus of its downward movement. I

The particular form of plunger 10 which is illustrated in greater detail in FIG. 2, is that disclosed in the aforesaid application of Everett D. McMurry, Serial No. 585,-- 881, now Patent No. 2,878,754. It will be understood;

however, that the details of the free piston or plunger, as a whole, except for the sealing ring construction, does not form a part of the present invention, since it is contemplated that the sealing rings herein disclosed will be applicable to plunger constructions of various types.

In accordance with the illustrative embodiment, the plunger comprises a generally cylindrical housing or body having an axial bore 16. Body 15 is externally threaded at 17 at its upper end to receive a tubular head 18 having ports 19 through the wall thereof near its upper end and provided at its upper end with a fishing head 20 by which the tool may be withdrawn from the well by conventional fishing tools in the event it does not return to the surface for one reason or another. At its lower end body 15 is also externally threaded at 21 to receive a tubular valve housing 22, the lower end of body 15 forming a downwardly facing annular seat 23 in the bore 24 of the valve housing. The latter is provided at a point below seat 23 with ports 25 which provide communication between bore 24 and the exterior of the plunger.

A valve stem 26 is mounted in the bore of the plunger for longitudinal movement therein and has an overall length substantially greater than the overall length of the plunger. Valve stem 26 is made up of an upper section 27 and a lower section 28 threadedly connected together at 29. The lower section 28 is provided at its upper end with an enlarged portion 30 forming a valve positioned for opening and closing the bore of seat 23 in response to longitudinal movements of the valve stem. An annular groove 31 is provided in the surface of lower stem section 28 intermediate the ends of the stem section and is adapted to receive a ball detent 32 which is mounted in the wall of valve housing 22 near its lower end and is yieldably projectible into bore 24 by means of a spring 32a. As illustrated in FIG. 2, the valve stem is in its upward position at which valve 30 is in closing engagement with seat 23, and groove 31 is above and out of engagement with detent 32. It will be understood that when the valve stem is moved downwardly sufliciently to position groove 31 opposite detent 32, the latter will project into groove 31 and yieldably lock the valve stem in the lowered position, thereby holding valve 30 away from seat 23, at which position the lower end of stem section 28 will project below the lower end of valve housing 22, as illustrated in FIG. 1.

The operation of the plunger, of the general form above-described, is well understood by those skilled in the art. With the form of plunger described, it will be evident that when the plunger descends in a well, valve stem 26 will be in the lowered position illustrated in FIG. 1, with valve 30 in the open position so that free passage of fluid through the bore of the plunger can occur as the plunger moves downwardly through the fluids in the well. When the plunger reaches the lower end of the well the projecting end of stem section 28 will strike stop 12, the resulting impact driving the stem upwardly to the position illustrated in FIG. 2, at which valve 30 closes bore 16. Pressure of the well fluids from below will hold the valve closed as the plunger is forced upwardly by the well fluid.

The seal-forming means of the present invention comprises a plurality of seal-forming elements in the form of rings 35 which are termed wobble washers, which are loosely positioned about body 15. Each of the rings 35 has an axial bore 36 which is of somewhat larger diameter than the external diameter of body 15. The external diameter of the rings is somewhat less than the internal diameter of tubing T, so that the rings may move laterally relative to the body. The amount of annular clearance between the rings and body 15 is such that a portion of the outer periphery of each ring will make contact with the interior wall of the tubing and with the exterior of body 15 through the opposite portion of the interior periphery of the ring. The rings are preferably constructed of metallic material, but also may be constructed of non-metallic materials, and the outer periphery of the rings are preferably rounded, as shown, to reduce the danger of having the rings hang up on projections which may be present on the tubing wall. At one end each of the rings is provided with a short boss 37 of lesser external diameter than the ring which serves as a spacer between one ring and the next. The overall thickness of each ring is relatively short, being usually from about 0.4 to 0.6 inch in thickness. The number of rings employed on a plunger may be varied widely, but in most instances from 20 to 40 rings will be employed on plungers of standard sizes.

In the embodiment illustrated in FIGS. 2 and 3, each of the rings has an annular recess 38 in its inner periphery which is adapted to form a seat for a spring 3? arranged in compression between the ring and the exterior of body 15 to urge the ring to an eccentric or radially off-set position relative to the longitudinal axis of body 15. Spring 39 may be of any suitable form adapted to per form this function. As illustrated, it is of generally circular form, split at one point, one end portion being bent inwardly to form a transverse segment 40 which is provided with an inwardly projecting lobe or boss 41 adapted to bear against the exterior of body 15. The spring shape and arrangement is such as to yieldably urge the ring radially toward the tubing wall in a direction determined by the point of contact of the spring with body 15; that is, the outer periphery of the ring will be urged toward the tubing wall while the inner periphery of the ring will be urged into contact with the exterior of the body 15 opposite the point of engagement of the spring with body 15.

It will be seen that by thus spring-loading the rings,- they will, as noted, be subjected to a positive force urging the rings into engagement with the wall of the tubing and the exterior of body 15. By angularly orienting the points of contact of the springs with body 15 about the latter, the points of contact of the rings with the tubing and body 15 can be caused to overlap sufficiently to effectively seal the annular space between the tubing wall and the body. The action of the springs will maintain the sealing contact of the rings between the body and the tubing wall, but upon engagement of projections in the tubing by the rings, they will yieldably retract suf ficiently to allow the rings to pass such projections. By providing the positive force available in the springs, stream-lining, due to the flow of fluids in the well bore, will be obviated. Also, where paraflfin tends to accumulate along the walls of the tubing, the rings will yield or retract sutficiently to pass these accumulations without assuming a stream-lining position on body 15.

FIG. 8 illustrates a modification of the embodiment previously described, differing from that illustrated by FIGS. 2 and 3, in that body 15 is provided with a plural ity of angularly spaced longitudinal grooves 42 in which spring lobes or bosses 41 may be seated and thus serve to fix the relative angular position of the several rings on body 15. As illustrated, four grooves spaced apart are shown and by alternating the angular positions of the rings correspondingly, it will be seen that the portions of the rings in contact with the tubing wall and with the exterior of body 15 will be oriented at angles of 90 to each other, and will overlap one another. It will be understood that any other orientation of the rings may be employed, as may be found desirable to assure substantial closing of the annular space between the plunger and the tubing Wall.

FIGS. 4 and 5 illustrate a modification of the sealing rings and the means for yieldably positioning them at different angles to each other. In this modification each of the rings is magnetized in a conventional manner to form north and south poles at diametrically opposite points thereon. As so magnetized, when the rings are assembled on body 15, the north pole of one ring will be positioned adjacent the south pole of the next adjacent ring, and this alternate north and sourth arrangement is maintained throughout the complete assembly of rings. However, the springs 39 in the several rings will be angularly oriented with respect to the poles so that when placed about body 15 the portions of the rings which engage the tubing wall and body 15 will form a substantial complete closure for the annular space between body 15 and tubing T. By magnetizing the rings, as described, the magnetic attraction between adjacent rings will maintain the rings in the angular orientation determined by the positions of springs 39. With this arrangement, the angular positions of the several rings can be maintained without grooving the exterior of 'body 15, as illustrated in FIG. 8. Again, however, it will be noted that springs 39 provide positive but yieldable force, urging the rings to the desired angular positions.

FIGS. 6 and 7 illustrate still another modification in which magnetic force is employed to positively but yieldably urge the rings in the desired relative angular directions, this force being provided by means of magnets. In this embodiment, a number of small permanent magnets 45 are mounted in radial openings 46 provided in the wall of body 15, the outer ends of Openings 46 being larger in diameter than magnets 45 to provide annular airgaps 47 about the outer ends of each of the magnets. Rings 35 will be constructed of steel or other suitable magnetically permeable material which will, therefore, be attracted to magnets 45. With this arrangement, the attraction of the magnets 45 will act to draw the portions of the rings opposite the magnets toward body 15, there by urging the opposite exterior portions of the rings against the wall of tubing T. These magnets 45 are angularly displaced with respect to one another about body 15 so that the several rings will be urged at difierent angles into over-lapping sealing contact between tubing T and the exterior of body 15. The magnets 45 do not need to be very strong. Their strength should be sufficient to draw the rings into contact with body 15 while permitting the rings to be thrust away from the magnets upon engagement with projections on the wall of tubing T It will be understood from the foregoing that various means may be provided for positively but yieldably urging the rings into radially off-set or eccentric positions with respect to the longitudinal axis of body 15 whereby to position the rings in sealing engagement between body 15 and the inner wall of tubing T, in order to provide the desired seal between the plunger and the body.

It will be understood that various alterations and modifications may be made in the details of the illustrative embodiment within the scope of the appended claims, but without departing from the spirit of this invention.

What we claim and desire to secure by Letters Patent is:

l. A well plunger of the free piston type, comprising, a tubular body adapted to be inserted in a well tubing for longitudinal movement therein, a plurality of continuous ring-shaped elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slida-ble seal between the body and the tubing, and elastic means arranged between the body and the elements to yieldably urge the elements to positions laterally off-set with respect to the axis of the body.

2. A well plunger of the free piston type, comprising, a tubular body adapted to be inserted in a well tubing for longitudinal movement therein, a plurality of continuous ring-shaped elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slidable seal between the body and the tubing, and resilient means mranged between the body and the elements to yieldably urge the elements to positions laterally ofi-set with respect to the axis of the body.

longitudinal movement therein, a plurality of continuous ring-shaped elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slidable seal between the body and the tubing, and magnetic means arranged between the body and the elements to yieldably urge the elements to positions laterally ofi-set with respect to the axis of the body.

5. In a well plunger according to claim 4, wherein said magnetic means comprises a permanent magnet positioned at a point on the body opposite each of said elements, said elements comprising magnetically attractible material.

6. A well plunger of the free piston type, comprising, a tubular body adapted to be inserted in a well tubing for longitudinal movement therein, a plurality of continuous ring-shaped elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slid-able seal between the body and the tubing, and elastic means arranged between the body and the elements to yieldably urge the ele ments to positions laterally off-set with respect to the axis of the body and angularly ofif-set with respect to one another.

7. In a well plunger according to claim 6, wherein said means comprises springs disposed in compression between said elements and angularly spaced points on the body.

8. In a well plunger according to claim 5, wherein said means comprises a permanent magnet positioned at a point on the body opposite each of said elements, said magnets being angularly spaced about said body, and said elements comprising magnetically attractible material.

9. In a well plunger according to claim 5, wherein said body has angularly spaced longitudinally extending grooves, and said means comprises springs disposed in compression between said elements and said grooves.

10. A well plunger of the free piston type, comprising, a tubular body adapted to be inserted in a well tubing for longitudinal movement therein, a plurality of continuous ring-shaped elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slidable seal between the body and the tubing, resilient means arranged between the body and said elements to yieldably urge the elements to positions laterally ofi-set with respect to the axis of the body and angularly elf-set with respect to one another, and magnetic means arranged on the elements to main tain said elements in said angularly oiI-set positions.

11. A well plunger of the free piston type, comprising, a tubular body having an axial bore therethrough and adapted to be inserted in a well tubing for longitudinal movement therein, valve means in said bore adapted to control the passage of fluid therethrough, a plurality of axially abutting continuous ring-shaped elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slidable seal between the body and the tubing, and elastic means arranged between the body and the elements to yieldably urge the elements to positions laterally ofi-set with respect to the axis of the body.

12. A well plunger according to claim 11, wherein said means comprises a spring means disposed in compression between each element and a point on said body.

13. A well plunger of the free piston type, comprising, a tubular body adapted to be inserted in a well tubing for longitudinal movement therein, a plurality of ring elements mounted about the body with a degree of annular clearance to permit lateral and angular shifting of the elements relative to the longitudinal axis of the body and to each other to form a slidable seal between the body and the tubing, the portion of the external periphery of each element which engages the tubing defining an axially and circumferentially uninterrupted surface, and elastic means arranged between the body and the elements to yieldably urge the elements to positions laterally oil-set with respect to the axis of the body.

14. In a well plunger according to claim 13, wherein said surface of said portion of the external periphery of each element is rounded in axial cross-section.

References Cited in the file of this patent UNITED STATES PATENTS Humason et al Mar. 14, 1922 Akeyson May 26, 1925 Lemmon Nov. 6, 1928 Burgher May 14, 1935 Pratt Dec. 14, 1943 Hammer Mar. 15, 1949 

